Service transmission in a packet data network

ABSTRACT

A method of transmitting a service to several subscribers in a packet data network capable of individual and group transmissions. The method comprises the steps of 1) collecting requests for the service from the several subscribers (MN 1 , MN 2 ), 2) evaluating the popularity of the service, 3) forming a group (G) of the subscribers that have requested the service, and 4) transmitting the service over a group transmission if the popularity of the service at least equals or is likely to equal a predetermined threshold level. The mobile node (MN) subscribers may be reached via several different access networks (AN), in which case an optimal access network can be selected. The method is preferably implemented by means of a group forming unit (GFU) which can be integrated or co-located with a gateway (GW) which connects the service provider&#39;s network (SNW) with the Internet.

[0001] This is a Continuation of International Application No.PCT/FI00/01165, which was filed on Dec. 29, 2000 in the English languageand designated the U.S.

BACKGROUND OF THE INVENTION

[0002] The invention relates to traffic management in a packet datanetwork having group transmission capability. A transmission group canbe formed, for example, by broadcasting or multicasting an encryptedtransmission signal and by distributing decryption keys only to theintended recipients (the group members). The packet data network is usedfor conveying several services to several subscribers. Some services aremore popular than others.

[0003] The invention is especially applicable to a multi-bearer packetdata network. A multi-bearer network, or an MBN, is a network having thecapability to carry a data packet via one of several alternativebearers. To be more precise, the term ‘multi-bearer network’ should beinterpreted as meaning ‘multi-bearer-type network’, or in other words, anetwork arrangement which provides multiple, different bearer types fordata packet delivery. An example of a suitable MBN is a so-called MEMOconcept (Multimedia Environment for Mobiles), see reference 1.Additionally, the MBN supports mobility of a subscriber terminal. Anexample of terminal mobility is IP mobility, which is the topic ofstandard RFC2002 by the Internet Engineering Task Force (IETF). This RFCstandard is incorporated herein by reference.

[0004] The problem underlying the invention is how to optimize the useof transmission resources. This problem is most significant in a packetradio network, because radio bandwidth is a limited natural resource.Broadcast systems based on orthogonal frequency division multiplexingmodulation (OFDM) and on single frequency network (SFN) techniques arevery efficient when the same signal is distributed to a large group ofsubscribers.

BRIEF SUMMARY OF THE INVENTION

[0005] Accordingly, it is an object of the present invention to providea mechanism for improving the efficiency of a packet data networkarrangement capable of individual and group transmissions when thenetwork arrangement is used for transmitting a service to severalsubscribers. The object is achieved with the method and the equipmentwhich are characterized by what is disclosed in the attached independentclaims. Preferred embodiments of the invention are disclosed in theattached dependent claims.

[0006] The invention is based on the idea that the overall transmissionefficiency of a packet data network can be improved by evaluating thepopularity of the services offered by/via the network, and if thepopularity exceeds a certain threshold value, the service is transmittedas a group transmission, and otherwise as one or more individual(point-to-point) transmissions. From this wording, it is apparent that‘individual’ or ‘point-to-point’ transmission means that each datapacket is dedicated to only one mobile node. ‘Group transmission’, asused herein, is a generic term for techniques in which data packets areintended to a group comprising two or more subscribers. Broadcasting andmulticasting are common examples of group transmissions.

[0007] The seemingly simple idea of the invention involves severalcomplexities. In other words, at first sight the invention appears tocause more problems than it solves. For instance, it is highly unlikelythat a large enough group of subscribers will request a servicesimultaneously. This means that in practice, group formation willinvolve delays. Some applications and some subscribers tolerate longerdelays than others. The subscribers should be able to indicate that theyare willing to join a group if joining the group causes a certainmaximum delay and/or allows a certain minimum price deduction overpoint-to-point transmission. According to a preferred embodiment of theinvention, this problem (delays and price issued versus subscriberpreferences) is solved by evaluating subscription profiles whichindicate on what terms each mobile node subscriber is willing to sufferadditional delays. The contents of the profiles differ between differentapplication types. For example, a file download may, in some situations,tolerate delays up to several hours. In contrast, an investor may not bewilling to wait more than a few seconds for an important piece of news.Thus, the network operator or server administrator may set upnetwork-wide or server-wide default profiles which indicate the maximumallowable delay for each application type. The profiles may also differbetween different subscribers. The subscriber-specific profiles overridethe network-wide or server-wide default profiles. Yet further, asubscriber should be able to indicate if a certain situation requires adeviation from the subscriber-specific profile (which in turn indicatesa deviation from the network-wide or server-wide default profiles). Sucha temporary deviation can be indicated by including a correspondingparameter in the actual service request.

[0008] The step of evaluating service popularity can be implementedsimply by comparing the actual number of pending requests with athreshold level. The threshold level may be fixed or adaptive. Anexample of an adaptive threshold level is a case where the thresholdlevel for forming a group in a broadcast network is increased as theload of that network increases. In addition to the actual number ofpending requests, the history of the service popularity and/or the typeof the service can be taken into account. For example, for some servicetypes, a group can be formed for a single subscriber, and moresubscribers can be added to the group later. An example of such aservice is file download, if the download protocol allows the downloadto begin at an arbitrary position of the file. Another example isreal-time video wherein the subscriber wants to see what is happeningnow, instead of requesting transmission from the beginning of theprogram. (Some video sources do not even have a ‘beginning’. Forexample, ski resorts or golf courses may offer real-time video of thecurrent weather conditions.) With such services, if the history showsthat the service has been popular, a group may be formed although itinitially consists of only one subscriber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0009] The method and the apparatus according to the invention will bedescribed more in detail by means of preferred embodiments, withreference to the appended drawing in which:

[0010]FIG. 1 is a block diagram of a network arrangement in which theinvention can be used and a group formation unit according to theinvention;

[0011]FIG. 2 shows an alternative location for the group formation unit;

[0012]FIG. 3 shows a signalling diagram which relates to group forming;

[0013]FIGS. 4A and 4B illustrates a decision-making process related togroup forming; and

[0014]FIG. 5 illustrates the concept of service profile hierarchy.

DETAILED DESCRIPTION OF THE INVENTION

[0015]FIG. 1 is a block diagram of a network arrangement in which theinvention can be used. Mobile nodes MN1, MN2 request services from oneor more servers Srv1, Srv2. The mobile nodes can access the services viaseveral alternative access networks AN. In the example shown in FIG. 1,the access networks comprise digital video broadcasting (DVB), digitalaudio broadcasting (DAB) and general packet radio service (GPRS). Othertypical access networks are high-speed GSM and wideband-CDMA (e.g.UMTS). In this example, the servers Srv1 and Srv2 are connected to aservice network SNW, which may be a service provider's local areanetwork, for example. The service network SNW is connected to theInternet via a gateway GW (and, typically, via a firewall which is notshown separately). The access networks are connected to the Internet viacorresponding routers R_(AN), where ‘AN’ is the abbreviation of theaccess network.

[0016] The invention is particularly useful in a network arrangementwith multiple alternative access networks, as shown in FIG. 1. However,the invention is applicable to a network arrangement with only oneaccess network, such as the GPRS network, as long as the access networkis capable of individual (point-to-point) and group transmissions.

[0017] According to the hardware aspect of the invention, the servicenetwork SNW comprises or is operationally connected to a group formationunit GFU. The group formation unit GFU collects or monitors servicerequests from the mobile node subscribers. It evaluates the popularityof the service. If the popularity of the service equals or exceeds apredetermined threshold level, the GFU forms a group of the subscribersthat have requested the service and transmits (or controls thetransmission of) the service over a group transmission. If thepopularity of the service fails to equal the predetermined thresholdlevel, the GFU transmits (or allows/controls the transmission of) theservice over a sufficient number of individual transmissions. In theexample shown in FIG. 1, the group formation unit GFU is integrated orco-located with the gateway GW. In this case, if the criteria for groupformation are met, the GFU requests the gateway GW to associate thegroup members with the group. It also requests the appropriateservice-providing server Srv1 or Srv2 to send the service to the gatewayGW such that the destination field of the data packets indicate thisgroup as the recipient.

[0018]FIG. 2 shows a slightly modified example in which the groupformation unit GFU is integrated or co-located with a service-providingserver Srv1. In this case, if the criteria for group formation are met,the GFU/Srv1 combination applies source routing to the correspondingrouter of the appropriate access network. In other words, if subscribersin the DAB network generate enough service requests for a certainservice in the server Srv1, the GFU/Srv1 combination directly transmitsthe service to the router R_(DAB) which forwards the service as a group(e.g. multicast) transmission.

[0019]FIG. 3 shows a signalling diagram which relates to group forming.In step 3-2, mobile node MN1 sends a service request SR1 comprising (forthe purposes of this example) four fields F1 to F4. The F1 field is anetwork layer header indicating the sender and the destination of theservice request, and the encapsulation protocol used. The F2 fieldcomprises available router information (RI). It indicates which routers(or access networks) can be used to deliver the requested service. TheF3 field is, or indicates, a user service profile USP, which will bediscussed in more detail later (see FIG. 5). The F4 field of the servicerequest comprises the packet data units PDU which indicate which serviceis being requested, such as the delivery of a certain file or an audiostream. In the scenario shown in FIG. 3, it has been assumed that theservice request SR1 from mobile node MN1 is the first pending requestfor a given service of server Srv1. The mobile node MN1 sends theservice request SR1 to server Srv1 but the group formation unit GFUtemporarily keeps the service request SR1 to itself. The service requestSR1 indicates that MN1 can be accessed via routers R_(GPRS) and R_(DAB)and R_(DVB).

[0020] In step 3-4, the group formation unit GFU logs the servicerequest and the available router information RI, and starts a timer witha time-out period of T. In step 3-6, within the time-out period T,mobile node MN2 requests the same service by sending a service requestSR2. The request SR2 differs from the request SR1 in that SR2 indicatesMN2 as the sender and only R_(GPRS) and R_(DAB) as available routers.(The user service profiles USP may differ, but it does not matter forthis scenario.) In step 3-8, the GFU notices another request for thesame service. Let us further assume (for keeping FIG. 3 simple) that twois a sufficient number for forming a subscriber group. Thus in step3-10, the GFU forms a multicast group G in its own memory. The group Guses router R_(DAB) because the access network under this router offersthe fastest transmission among access networks which are common to bothgroup members MN1 and MN2. In step 3-12, because R_(DAB) has beenselected as the fastest common router, the GFU orders router R_(DAB) toconfigure its routing tables such that a new group G consists of mobilenodes MN1 and MN2. In steps 3-14 and 3-16, the GFU informs MN1 and MN2,respectively, that they are members of the group G in the DAB network.The messages 3-14 and 3-16 include the necessary security-related data,such as the necessary decryption keys (if needed).

[0021] In step 3-18, when the group G is formed, the GFU requests thegateway router GW to associate the group G with router R_(DAB). Next, instep 3-20, the GFU forwards a service request SR to the server Srv1.This service request naturally requests the service which was requestedby both MN1 and MN2. In step 3-22, the server Srv1 responds by startingto send packet data units PDU_(S) to the gateway GW, which forwards themto the router R_(DAB). Finally, in step 3-24, the router R_(DAB)transmits packet data units PDU_(S) of the requested service as onegroup transmission to the group G.

[0022]FIG. 4A illustrates a decision-making process related to theformation of subscriber groups for group transmission. The horizontalaxis 41 represents quantified time and the vertical axis 42 representsservice requests per unit of time. This means that the group formingunit GFU counts the number of service requests for each service once perunit of time (such as one second). The vertical bars 43 represent thenumber of service requests during each unit of time. In this example,two subscribers requested a certain service during the first second,seven during the next second, etc. The curve 44 depicts the thresholdlevel for forming a transmission group. When the first subscriberrequests the service, the GFU starts a timer with a period of T. Whenthe timer expires, the GFU notices that the cumulative number ofrequests, shown with reference number 45, is fifteen. This exceeds thethreshold level 44, and the GFU forms a new subscriber group. Then theprocess is repeated, and reference number 45′ depicts a second instantwhen the next group is formed, and so on.

[0023] In FIG. 4A, the threshold level 44 is not fixed but adaptive. Thethreshold level for forming a group in a broadcast network can beincreased or decreased as the load of that network increases ordecreases, respectively. In addition the threshold level may have anabrupt change 46 at certain points of time, such as after businesshours.

[0024]FIG. 4B shows a variation of the scenario shown in FIG. 4A. Thedifference between FIGS. 4A and 4B is that in the latter, the GFU knowsthat the service is of a type which allows new members to be added to anexisting group. In this case, the GFU does not have to wait through thetime window T before forming a group, and reference number 47 indicatesa point of time where the cumulative number of subscribers (nine)exceeds the threshold level 44. In the earlier scenario, shown in FIG.4A, the GFU could have formed the group at the instant depicted byreference number 47 (without waiting through the time window T), but itdid not do so because it wanted to maximize the size of the broadcastgroup which could not be extended afterwards.

[0025] How does the GFU know which services or service types allow newmembers to be added to an existing group? The specification of Internetprotocol version 6 (IPv6) defines optional headers which can be used toindicate such parameters. If IPv4 is used, a rule of thumb is thatservices using UDP (User Datagram Protocol) allow new members to beadded to an existing group, whereas services using TCP (TransmissionControl Protocol) do not.

[0026]FIG. 5 illustrates the concept of service profile hierarchy. Thenetwork operator or the GFU administrator can set up a network-wide orserver-wide default service profile PR0 which indicates the maximumallowable delay (in seconds) for several application types, four ofwhich are shown in FIG. 5. Subscriber-specific service profiles PR1,PR2, . . . , relate to the subscribers of the mobile nodes MN1, MN2,etc. In this example, the subscriber-specific service profile PR1 doesnot have an entry for news/text or news/video, which means that thesubscriber is satisfied with the corresponding default values of thedefault profile PR0. However, this subscriber is willing to toleratelonger delays in the hope of obtaining lower transmission costs, asindicated by the long maximum delay times for entertainment video andfile download. Let us further assume that FIG. 5 shows an extraordinarysituation in which the subscriber cannot tolerate the half-hour delayindicated by the profile PR1, and the user service profile USP sentalong with the service request SR1 (cf. step 3-2 and field F3 in FIG. 3)indicates a maximum delay of 10 seconds. Thus the logic for the GFU isto use the rightmost profile which has an entry for the application typein question.

[0027] Moreover, some services are possible only in certain accessnetworks. For example, the GPRS network is not suitable for transmittinglive video streams. Thus, the default service profile PR0 (or some otherdata structure) should indicate which access networks are capable ofconveying the service in question.

[0028] The profiles PR0, PR1, PR2 and USP shown in FIG. 5 are verysimplistic in that the only indicated parameter is the maximum allowabledelay until the beginning of group transmission. In practice, theprofiles can have many more parameters, such as maximum allowable priceper minute and/or minimum price deduction which must be achieved inorder to use group transmission. Thus, the network operator, or theservice provider or the GFU administrator faces yet another problem: howto optimize group formation? If the threshold for group formation islow, and many groups are formed in the broadcast networks, the broadcastnetworks may run out of resources. There are at least two approaches tothis problem, namely resource optimization and resource re-allocation.

[0029] Resource optimization means that the available resources (thetransmission capability) are used in a manner which maximizes theoperator's profits. A field of mathematics known as linear programmingaddresses the problems of resource optimization. Many linear programmingalgorithms are recursive, which means that the computation timeincreases according to the factorial of the number of resources. U.S.Pat. No. 4,744,028 to Narendra Karmarkar discloses a linear programmingalgorithm which is not recursive and which is especially suited tooptimizing resources in a telecommunication system.

[0030] Resource re-allocation means that the resources available to thenetwork operator(s) are not fixed. In other words, the networkoperator(s) may adjust the resources allocated to the various accessnetworks. In practice this means that at least two different accessnetworks are owned or administered by a single operator (or severaloperators in cooperation), and that the one or more operators are ableto adjust the bandwidth allocated to the access networks as needed. Ifseveral operators are involved, one of them can sell surplus capacity toanother. This obviously requires that if one access network surrenders acertain frequency band, another access network is able to utilize thatband.

[0031] The description only illustrates preferred embodiments of theinvention. The invention is not, however, limited to these examples butit may vary within the scope of the appended claims. For example, agroup may be formed on the basis of an estimate (an educated guess) thatthe service will be popular. Thus, for example, news can be broadcast ata certain time without actually measuring the popularity of the service.

[0032] Reference

[0033] 1. MEMO network documentation at http://memo.lboro.ac.uk

1. A method of transmitting a service to several subscribers in a packetdata network capable of individual and group transmissions, the methodcomprising the steps of: collecting (3-4) requests for the service (SR1,SR2) from the several subscribers (MN1, MN2), evaluating (3-8) thepopularity (45) of the service, forming (3-10, 3-12) a group (G) of thesubscribers that have requested the service, and transmitting (3-20 . .. 3-24) the service over a group transmission if the popularity of theservice (45, 45′ 47) at least equals or is likely to equal apredetermined threshold level (44), and transmitting the service overone or more individual transmissions if the popularity of the servicefails to equal the predetermined threshold level.
 2. A method accordingto claim 1, wherein the packet data network comprises or is connected toseveral different access networks (AN), and the step of transmitting theservice over a group transmission comprises selecting an optimal accessnetwork.
 3. A method according to claim 2, wherein the access networks(AN) comprise broadcast networks, such as DAB and DVB, and networks withpoint-to-point transmission capability, such as GSM, GPRS and UMTS.
 4. Amethod according to any one of the preceding claims, further comprisingadjusting resources allocated to the access networks (AN) on the basisof service popularity of several services transmitted via the accessnetworks.
 5. A method according to any one of the preceding claims,wherein the group forming step comprises evaluating a subscriptionprofile (PR0 . . . PR2, USP) for each subscriber that has requested theservice.
 6. A method according to any one of the preceding claims,wherein the step of evaluating service popularity comprises evaluatingthe current value and the history of the popularity.
 7. A methodaccording to claim 6, wherein the step of group forming comprises:evaluating the type of the requested service, and forming a groupalthough the initial number of subscribers in that group does not equalthe predetermined threshold level, if: a) the type indicates thatsubscribers can be added to an existing group, and b) the history of thepopularity indicates that the popularity is likely to equal thepredetermined threshold level.
 8. A group forming unit (GFU) forassisting transmission of a service from a server (Srv1, Srv2) toseveral subscribers in a packet data network capable of individual andgroup transmissions, wherein the group forming unit is adapted to:collect (3-4) requests for the service (SR1, SR2) from the severalsubscribers (MN1, MN2), evaluate (3-8) the popularity (45) of theservice, form (3-10, 3-12) a group (G) of the subscribers (MN1, MN2)having requested the service, and to configure transmission (3-20 . . .3-24) of the service over a group transmission if the popularity of theservice (45) at least equals or is likely to equal a predeterminedthreshold level (44), and otherwise over one or more individualtransmissions.
 9. A group forming unit (GFU) according to claim 8,wherein the packet data network comprises or is connected to severaldifferent access networks (AN), and group forming unit (GFU) is adaptedto select an optimal access network.
 10. A group forming unit (GFU)according to claim 9, wherein the group forming unit is integrated orco-located with a gateway (GW) connecting a first network (SNW), towhich the server (Srv1, Srv2) is connected and a second network (11)which is common to the access networks (AN).
 11. A group forming unit(GFU) according to claim 9, wherein the group forming unit is integratedor co-located with the server (Srv1) which provides the requestedservice.
 12. A method of transmitting a service to several subscribersin a packet data network that comprises or is connected to severaldifferent access networks (AN) and is capable of individual and grouptransmissions, the method comprising the steps of: collecting (3-4)requests for the service (SR1, SR2) from the several subscribers (MN1,MN2), evaluating (3-8) the popularity (45) of the service, selecting anoptimal access network, transmitting the service over one or moreindividual transmissions if the popularity of the service fails to equalthe predetermined threshold level, forming (3-10, 3-12) a group (G) ofthe subscribers that have requested the service, and transmitting (3-20. . . 3-24) the service over a group transmission if the popularity ofthe service (45, 45′ 47) at least equals or is likely to equal apredetermined threshold level (44), and adjusting resources allocated tothe several different access networks (AN) on the basis of servicepopularity of several services transmitted via the access networks. 13.A method of transmitting a service to several subscribers in a packetdata network capable of individual and group transmissions, the methodcomprising the steps of: collecting (3-4) requests for the service (SR1,SR2) from the several subscribers (MN1, MN2), evaluating (3-8) thepopularity (45) of the service, wherein service popularity comprises acurrent value and a history of the service popularity, transmitting theservice over one or more individual transmissions if the popularity ofthe service fails to equal the predetermined threshold level, forming(3-10, 3-12) a group (G) of the subscribers that have requested theservice, and transmitting (3-20 . . . 3-24) the service over a grouptransmission if the popularity of the service (45, 45′ 47) at leastequals or is likely to equal a predetermined threshold level (44),wherein the step of group forming comprises: evaluating a type of therequested service to check if subscribers can be added to an existinggroup, and forming the group although the initial number of subscribersin that group does not equal the predetermined threshold level, if: a)the type indicates that subscribers can be added to an existing group,and b) the history of the popularity indicates that the popularity islikely to equal the predetermined threshold level.
 14. A group formingunit (GFU) according to claim 8, wherein the group forming unitcomprises: means for evaluating a type of the requested service to checkif subscribers can be added to an existing group, and means for formingthe group although the initial number of subscribers in that group doesnot equal the predetermined threshold level, if: a) the type indicatesthat subscribers can be added to an existing group, and b) the historyof the popularity indicates that the popularity is likely to equal thepredetermined threshold level.